title: Phosphorylation of eIF4GII and 4E-BP1 in response to nocodazole treatment: a reappraisal of translation initiation during mitosis.
abstract: Translation mechanisms at different stages of the cell cycle have been studied for many years, resulting in the dogma that translation rates are slowed during mitosis, with cap-independent translation mechanisms favored to give expression of key regulatory proteins. However, such cell culture studies involve synchronization using harsh methods, which may in themselves stress cells and affect protein synthesis rates. One such commonly used chemical is the microtubule de-polymerization agent, nocodazole, which arrests cells in mitosis and has been used to demonstrate that translation rates are strongly reduced (down to 30% of that of asynchronous cells). Using synchronized HeLa cells released from a double thymidine block (G 1/S boundary) or the Cdk1 inhibitor, RO3306 (G 2/M boundary), we have systematically re-addressed this dogma. Using FACS analysis and pulse labeling of proteins with labeled methionine, we now show that translation rates do not slow as cells enter mitosis. This study is complemented by studies employing confocal microscopy, which show enrichment of translation initiation factors at the microtubule organizing centers, mitotic spindle, and midbody structure during the final steps of cytokinesis, suggesting that translation is maintained during mitosis. Furthermore, we show that inhibition of translation in response to extended times of exposure to nocodazole reflects increased eIF2α phosphorylation, disaggregation of polysomes, and hyperphosphorylation of selected initiation factors, including novel Cdk1-dependent N-terminal phosphorylation of eIF4GII. Our work suggests that effects on translation in nocodazole-arrested cells might be related to those of the treatment used to synchronize cells rather than cell cycle status.
authors.affiliation: Centre for Biological Sciences; University of Southampton; Southampton, UK.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Coldwell
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Cowan
authors.forename: Markete
authors.initials: M
authors.lastname: Vlasak
authors.forename: Abbie
authors.initials: A
authors.lastname: Mead
authors.forename: Mark
authors.initials: M
authors.lastname: Willett
authors.forename: Lisa S
authors.initials: LS
authors.lastname: Perry
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Morley
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology*; D016203:CDC2 Protein Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D018797:Cell Cycle Proteins; D048749:Cytokinesis / Q000187:drug effects; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D013058:Mass Spectrometry; D008938:Mitosis / Q000187:drug effects*; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology*; D010455:Peptides / Q000032:analysis; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D011804:Quinolines / Q000494:pharmacology; D016415:Sequence Alignment; D013844:Thiazoles / Q000494:pharmacology; D014404:Tubulin / Q000378:metabolism; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; C491300:EIF4G2 protein, human; D039603:Eukaryotic Initiation Factor-4G; D010455:Peptides; D010750:Phosphoproteins; D011804:Quinolines; C512984:RO 3306; D013844:Thiazoles; D014404:Tubulin; C583541:EIF2AK1 protein, human; D019892:eIF-2 Kinase; D016203:CDC2 Protein Kinase; D015739:Nocodazole
keywords: 4E-BP1; Cdk1; cell cycle; eIF4GII; eukaryotic translation initiation factor; nocodazole